[Dune] Major update for dune-alugrid: 2d version now also parallel.

[Robert Kloefkorn]

Over the past year the ALUGrid development team has improved the
implementation such that parallel simulations in 2d
are now also supported (kudos to Martin Alkämper).

At some point it was no longer possible to merge the new version with
the current master.
Therefore, the current master has been renamed to master-old and the
master has been overwritten with the updates.

Upon git pull you will get a lot of conflicts that can be resolved via:

git reset --hard origin/master

or, if you want to keep the old state for now

git checkout master-old

Please note: The code base of the 2d code has changed considerably, so
problems might occur although the new version has been tested
thoroughly. The new master supports the current 2.4 release and the
master of the dune core modules. For the 2.3 release the master-old has
to be used.

Best,

Rob